1. Field of the Invention
This invention relates to a process for the production of optical active alkoxybenzonitrile derivatives and optical active alkoxybenzoic acid derivatives which have utility as medicines, materials for liquid crystal or intermediates thereof.
2. Prior Art
It has been known that an optical active alkoxybenzonitrile having an optical active alkoxy group bonded through an oxygen atom to benzonitrile at the 4 position finds extensive use for materials of liquid crystal and medicines. However, there has not been developed a method for synthesizing such optical active compounds which can be utilized universally in a simple manner.
Williamson Method is known for synthesis of compounds having ether bonds as well as alkoxybenzonitrile in which method alkoxide is reacted with alkylhalide or alkyltosylate. However, the synthesis of an optical active alkoxybenzonitrile using this method accompanies a problem that an optical active alkylhalide and alkyltosylate used as a starting material can not be mass-produce in an inexpensive manner and particularly the former is susceptible to reduced optical purity. Furthermore, this synthesis method involves another problem that if an optical active secondary alkylhalide or alkyltosylate is used as a starting material the resulting compound is attached with a risk of reduction in optical purity depending upon kinds of the secondary alkyl groups and the reaction conditions because the reaction of Williamson method progresses in S.sub.N 2 reaction system and in this connection the asymmetric center becomes the reaction center.
On the other hand, Williamson Method is employed also for synthesizing an optical active alkoxy benzoic acid having an alkyl group bonding through an oxygen atom to the 4-position of benzoic acid by reacting 4-hydroxybenzoic acid or the ester thereof and an optical active alkylhalide or alkyltosylate under basic conditions. For instance, in a publication entitled "Liquid Crystals" 16.299 (1994), there is reported a method for synthesizing an optical active alkoxy benzoic acid by reacting tosylate derived from a variety of optical active secondary alcohol with methyl 4-hydroxy benzoic acid and hydrolyzing the resulting methyl alkoxybenzoate. However, the products derived from the method also encounter reduction of optical purity and involve with a problem that the preparation of an optical active alkyltosylate used as a starting material requires much expenditure.